Trim Gauge not working - Anyone?

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Apr 4, 2003
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61
I have a 91 OMC Cobra 3.0 Litre on a 91 Chris Craft 167 Concept. The trim gauge hasn't worked since I bought it 2 years ago. Any idea where i'd start to troubleshoot this? Should it be an easy fix? I can and have done without it if it's a high dollar and/or effort. Any thoughts?
 

Boatin Bob

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Sep 24, 2001
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Re: Trim Gauge not working - Anyone?

Greg...does it move at all with the key on? Not sure what you mean by doesn't work. I would say the most common problem for these is the sending unit on the leg, it's really like a rheostat that changes it's resistance as the leg moves up and down which in turn moves the needle in the guage. These units usually end up leaking and then the resistance changes causing the guage to not work or work improperley.
 
Joined
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Re: Trim Gauge not working - Anyone?

No it doesn't move when I turn the key on. Sounds like this is a common problem and if I fix it, it's just a matter of time before it happens again. I'll check it out thought. Any idea if that sending unit is in eyeball range somewhere or do I need to remove components to get to it?
 

MrBill

Senior Chief Petty Officer
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Aug 4, 2002
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Re: Trim Gauge not working - Anyone?

I approached the same issue last Summer and the people on this forum were very helpful. You're starting with the same expense<=>value trade-offs that I had so here's my experience...<br /><br />The diagnostics and wiring diagrams available in most manuals are extremely valuable, in my case the $25 Mercruiser manual was well worth the expense, along with the advice of Trent and others. I quickly traced my problems to the trim sending and limit switches, along with some improper wiring to the controls done by the former owner. The first thing to determine is whether the problems are mechanical, electrical or both. Going through that diagnostic is necessary.<br /><br />For me (with a 1989, 19 footer), I concluded that the cost and effort was not worthwhile mid-season. It would have meant $250 in parts, taking the boat out of the water and removal/replacement of the drive, along with the other maintenance that I wouldn't want to pass up when the boats out of the water. The weather was too good and I was having too much fun so I let it go. Many on the forum said it was too much of a pain in the neck to diagnose and repair, and they suggested learning to trim the boat by feel, sound and engine RPM was a better long-term solution. I now agree...but it's nice to get a handle on trim position when starting out or when you're in the shallows like I am a lot.<br /><br />If the trim features work well mechanically, chances are you're hunting an electrical issue like me. Before starting out check availability of some parts, I was happy to find out before starting the repair that the port limit assembly was no longer available...it made the decision to delay the repair much easier.
 

Boatin Bob

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Re: Trim Gauge not working - Anyone?

Greg...go to the Teleflex page to see some basic wiring and trouble shooting help. You should start at the guage to make sure it's working, when the key is on there should be power to the guage, measure with a mter or test light, if there is power then ground out the sending unit terminal, the guage should move all the way, if it does then your guage is OK and you have find the problem either in the wire or sending unit. To get to the sender the boat has to be out of the water, it's mounted on the stbd side of the transom bracket with 2 screws and has a spring loaded leg that follows the drive up and down. It has 2 wires(black) that go through the transom bracket around where the hydraulic tilt lines come out. The wire has a rubber grommet attached which seals the transom bracket and it attaches to a rubber plug usually around the rear of the engine. If you can find the plug then you can measure the resistance of the sender and if it's open or shorted then you know the sender is bad.<br /><br /> Trim Guage Page
 
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Re: Trim Gauge not working - Anyone?

Bill sounds like you confirmed what I suspected. I've used it 2 seasons withouth the gauge and I trim by feel more than a gauge anyway. I just thought it would be helfpul when starting up in shallow water to know when i'm far enough down to crank it up. I guess I can continue to just walk the 3 whole steps and look over the rear or ask a passenger.<br /><br />And Bob thanks for the response but for a boat repair neophite like myself I just have a one word answer - HUH? Haha I'll check around and see what I can see but you throw those part terms around like I know what they are. Must be nice to know that much about them. How much do you charge per hour? Haha
 

Boatin Bob

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Re: Trim Gauge not working - Anyone?

Well Greg....I'm on my 5th Cobra now (last 2 boats have had twins) so I think I've done this about 5 times over the last 12 years. At least with the Cobra you don't have to remove the drive to replace the sender, if you change your mind just post again because there are lots of people on this board just waiting to help!
 
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Re: Trim Gauge not working - Anyone?

Now you have my attention. If I had a better idea where to start looking. When I read your response, I can't put pictures in my mind with your words. Can you try again assuming that once I get past the propellor, I don't know what is what by it's official name. For example I wouldn't know a sender if it bit me. The other concern I have is finding the part even if I find a bad one. And I don't have a tester either but I guess I could borrow or buy one.
 

Boatin Bob

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Re: Trim Gauge not working - Anyone?

OK....I'm attaching a link to an online OMC parts catolog. When you get there select your year and next select your motor size and then scroll down and select transom mount, once in there look over on the right side under the box called transom seal kit and see item # 86, 88, etc, this is your trim sending unit. Keep this link as the online parts pictures can be very valuable. You can see this by looking at your from the right side looking at the back of the boat, easier to see if drive is lifted and turned. It's only held on by 2 hex screws (approx 1/4"). I would still test the guage first and then resistance check the sending unit from inside the boat before yoyu worry about the sending unit itself. If you can get to the back of the engine you will see the pair of black wires coming through the transom mount, just follow those up to the connector and unplug it there to test.OMC Parts Catolog
 
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